Methods and compositions for treating pain

ABSTRACT

Methods and compositions for treating pain are disclosed. The compositions are based on dry powders comprising microparticles of diketopiperazines and an analgesic active agent. The analgesic in the compositions comprises one or more peptide analgesics or derivatives thereof, which are administered to a subject using a pulmonary inhalation drug delivery system comprising a dry powder inhaler and the analgesic composition. The present compositions produce fewer side effects associated with current opioid therapy.

RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No. 14/354,092, filed Apr. 24, 2014, which is a 371 of PCT/US2012/061749, filed Oct. 24, 2012, which claims benefit from U.S. Provisional Patent Application Ser. No. 61/550,860, filed Oct. 24, 2011, the contents of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

Methods and compositions for treating pain, such as inhaled opioid compositions, are disclosed. Exemplary compositions can comprise dry powders for pulmonary inhalation.

BACKGROUND

Acute pain is characterized by a sudden onset and relatively short duration, and is generally treated with opioid analgesics like morphine. Morphine and similar opioid analgesics suppress the perception of pain by reducing the number of pain sensations sent by the nervous system and the brain's reaction to those pain signals. Current opioid therapy using morphine and like compounds are effective to treat pain but the side effects they produce such as addiction, somnolence, tolerance, respiratory depression, and constipation limit their clinical use.

In addition, opiates presently used in therapy such as morphine are alkaloid compounds isolated from natural sources such as the opium poppy. There are also semi-synthetic substances derived from the opium poppy, as well as and are chemically synthesized compounds including anilidopiperidines, phenylpiperidines, diphenylpropylamine derivatives, morphinan derivatives, and benzomorphan derivatives.

Opioid analgesics relieve pain and inhibit nociceptive signaling by binding to opioid receptors on cells in the central and peripheral nervous systems and the gastrointestinal tract. The analgesic effects of opioids are due to decreased perception of pain, decreased reaction to pain and increased resistance to pain. Known opioid receptors include mu (μ), delta (δ) and kappa (κ). Opioid receptor agonists, including morphine, the enkephalins, and the dynorphins, bind to these receptors. The most commonly studied opioid receptor modulated is the μ opioid receptor. However, kappa opioid receptor agonists have been shown to be effective and potent analgesics, but their usefulness in humans is limited due to their psychomimetic and dysphoric effects. Delta (δ) opioid receptor agonists are known to produce analgesic effects with lesser magnitude side effects than μ analgesics. For example, delta analgesics induce less tolerance and physical dependence, do not depress respiration, and cause few or no adverse gastrointestinal effects, including constipation. However, delta opioid receptor agonists can produce seizures. Moreover, in some animal experiments, delta opioid agonists can produce an effective and potent analgesic effect when administered intrathecally or by intracerebroventricular injection. However; these routes of administration are not practical for treating patients.

Therefore, there is still a need in the medical art to develop new treatments for pain which would facilitate patient therapy and reduce or eliminate unwanted side effects. Additionally, there is a need for the identification and development of new compounds and compositions that do not cross the blood-brain barrier and effectively alleviate pain without activating opioid receptors in the central nervous system.

SUMMARY

Methods and compositions for treating pain are disclosed. The compositions can comprise dry powders comprising microparticles including a diketopiperazine and an active agent. In an embodiment the microparticles are administered in compositions for pulmonary inhalation using a dry powder inhalation system and comprise one or more peptide analgesics or derivatives thereof delivered. In embodiments the diketopiperazine is an N-substituted-3,6-aminoalkyl-2,5-diketopiperazine. In certain embodiments the active agent can be a peptide, or the like.

In embodiments the diketopiperazine can be 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine wherein X is fumaryl, succinyl, glutaryl, maleyl, malonyl, oxalyl, or a pharmaceutically acceptable salt thereof, such as bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.

An embodiment includes an inhalable, analgesic composition comprising microparticles of a diketopiperazine and a peptide comprising less than 20 amino acids; wherein said composition is effective in relieving pain. In an embodiment the peptide comprises one or more of: glycine, alanine, valine, methionine, phenylalanine, serine, threonine, asparagine, glutamine, cysteine, lysine, histidine, aspartic acid, glutamic acid, leucine, isoleucine, norleucine, tyrosine, serine, proline, and tryptophan. In some embodiments, the peptide comprises at least 3 amino acids, wherein each of those 3 amino acids is: arginine, phenylalanine, leucine, isoleucine, norleucine, tyrosine, serine, proline, or tryptophan. In embodiments the peptide is greater than 0.25% of the weight of a dry powder composition.

In certain embodiments the peptide can comprises an amino acid sequence of from three to eight amino acids in length. In embodiments the peptide can comprise one of the following sequences: (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1), (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2), Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4); Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), and Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).

In embodiments the peptide can be an opioid receptor agonist. In embodiments the peptide can bind to the μ opioid receptor, δ opioid receptor, or κ opioid receptors, or combinations of receptors thereof of cells in the central or peripheral nervous systems.

In embodiments the peptide can be an alpha-melanocyte stimulating hormone (MSH) receptor agonist.

In embodiments the composition can be a dry powder for inhalation and comprise microparticles having a volumetric mean geometric diameter less than 5.8 μm in diameter.

Certain embodiments comprise a method for treating pain, comprising administering to a subject in need of treatment a therapeutically effective amount of a composition described herein using a dry powder drug delivery system comprising a dry powder inhaler configured with a container to hold said analgesic composition in a containment configuration and in a dosing configuration. In embodiments the analgesic composition can be a dry powder comprising a peptide that binds to an opioid receptor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a graph showing data from 55° C. warm-water tail withdrawal (“Tail-flick”) experiments in mice treated with an inhalable dry powder formulation comprising an analgesic peptide at various concentrations administered by insufflation and compared to a control intraperitoneal injection of the peptide and a placebo dry powder formulation.

FIG. 2 depicts a graph showing data from 55° C. warm-water tail withdrawal (“Tail-flick”) experiments in mice treated with a inhalable dry powder formulation comprising a second analgesic peptide and different from that used in FIG. 1 in various amounts of peptide in the same amount of powder administered by insufflation and compared to a control intraperitoneal injection of the peptide and a placebo dry powder formulation.

FIG. 3 depicts a graph showing data from 55° C. warm-water tail withdrawal (“Tail-flick”) experiments in mice treated with an inhalable dry powder formulation comprising the second analgesic peptide used in FIG. 2 administered by insufflation and compared to an intraperitoneal injection of morphine.

FIGS. 4A and 4B are graphs showing data from experiments measuring spontaneous locomotion and respiration in the comprehensive laboratory animal monitoring system (CLAMS) using mice treated with an inhalable dry powder formulation comprising each of the peptides as described in FIGS. 1 and 2 and compared to a dose of inhalable morphine and blank FDKP powder as placebo. FIG. 4A shows data from ambulatory observations made and FIG. 4B shows data from respiratory measurements made from treated animals versus controls.

FIG. 5 depicts a graph showing data from conditioned place preference experiments using mice treated with an inhalable dry powder formulation comprising each of the peptides as described in FIGS. 1 and 2 and compared to a dose of inhalable morphine and blank FDKP powder as placebo.

DETAILED DESCRIPTION

Disclosed are methods and compositions for treating pain that facilitate delivery of the pain medication while reducing unwanted side effects, such as, for example, addiction, somnolence, tolerance, respiratory depression, and constipation, and the like.

In embodiments the pain to be treated can be, for example, a peripheral neuropathy, a central neuropathy, a traumatic abnormality, a cerebral vascular accident, postoperative pain, dental pain, direct trauma, infection, HIV infection, small pox infection, herpes infection, toxic exposure, exposure to arsenic, exposure to lead, cancer, invasive cancer, congenital defect, phantom limb pain, encephalitis, rheumatoid arthritis, fibromyalgias, spinal root lesions, spinal root impingement, back pain, multiple sclerosis, chronic pain, fibrous tissue pain, muscle pain, tendon pain, ligament pain, pain associated with diarrhea, irritable bowel syndrome, abdominal pain, chronic fatigue syndrome, and spasms.

In embodiments, the methods and compositions can be used for the treatment of pain modulated through cell receptors. In embodiments disclosed herein the methods and compositions can comprise, active agents such as, for example, receptor agonists, antagonists, or the like. In embodiments disclosed herein the methods and compositions can comprise, for example, opioid receptor agonists and/or antagonists, alpha-MSH receptor agonists and/or antagonists, and the like, and can be provided to a subject as the active agents for treating pain. In certain embodiments the active agents act directly or indirectly upon other receptor agonists.

As used herein “peptide” refers to an amino acid sequence, whether from naturally occurring sources, or from synthetic origin, connected by a peptide bond, having at least two (2) amino acids, which can be modified or derivatized by modifying groups. U.S. Pat. No. 5,610,271 discloses synthetic peptides that can associate with opioid receptors. This patent is incorporated herein by reference in its entirety for its disclosure related to synthetic peptides.

As used herein “analgesic peptide” refers to a peptide that when administered to a patient suffering with pain, can reduce pain sensations in the patient. Typically, the peptides herein comprise and amino acid sequence of less than 20 amino acids, such as less than 10 amino acids, or about 2 to 8 amino acids, and are capable of binding opioid receptors in the central nervous system.

As used herein “cell receptor” includes pain-related receptors.

As used herein, “diketopiperazine” or “DKP” includes diketopiperazines and salts, derivatives, analogs and modifications thereof falling within the scope of the general Formula 1, wherein the ring atoms E₁ and E₂ at positions 1 and 4 are either N and at least one of the side-chains R₁ and R₂ located at positions 3 and 6 respectively contains a substituted amino and/or carbonyl-containing group and a carboxylic acid (carboxylate) group. Compounds according to Formula 1 include, without limitation, diketopiperazines, diketomorpholines and diketodioxanes and their substitution analogs.

In some embodiments, R¹ has 1 to 20 carbon atoms or 4 to 12 carbon atoms; 1-6 oxygen atoms or 2-4 oxygen atoms; 0-2 nitrogen atoms; and any necessary hydrogen atoms. In some embodiments, R¹ is —R^(a)-G-R^(b)—CO₂H.

In some embodiments, R² has 1 to 20 carbon atoms or 4 to 12 carbon atoms; 1-6 oxygen atoms or 2-4 oxygen atoms; 0-2 nitrogen atoms; and any necessary hydrogen atoms. In some embodiments, R² is —R^(a)-G-R^(b)—CO₂H.

With respect to any relevant structural representation, such as —R^(a)-G-R^(b)—CO₂H, each R^(a) may independently be —(CH₂)_(a)—, wherein a is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

With respect to any relevant structural representation, such as —R^(a)-G-R^(b)—CO₂H, each G may independently be NH, CO, CO₂, CONH, or NHCO.

With respect to any relevant structural representation, such as —R^(a)-G-R^(b)—CO₂H, R^(b) may be —(CH₂)_(b)—; wherein b is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10; or a C₂₋₁₀ alkenylene, such as —CH═CH—, —CH₂CH═CH—, etc.

Diketopiperazines, in addition to making aerodynamically suitable microparticles, dissolve rapidly at physiologic pH thereby releasing the active agent for absorption into the circulation. Diketopiperazines can be formed into particles that incorporate a drug or particles onto which a drug can be adsorbed. The combination of a drug and a diketopiperazine can impart improved drug stability. These particles can be administered by various routes of administration. As dry powders these particles can be delivered by inhalation to specific areas of the respiratory system, depending on particle size. Additionally, the particles can be made small enough for incorporation into an intravenous suspension dosage form. Oral delivery is also possible with the particles incorporated into suspensions, tablets or capsules.

In one embodiment, the diketopiperazine is bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or 3,6-di(fumaryl-4-aminobutyl)-2,5-diketopiperazine (fumaryl diketopiperazine, FDKP). The FDKP can comprise microparticles in its acid form or salt forms which can be aerosolized or administered in a suspension.

In another embodiment, the DKP is a derivative of 3,6-di(4-aminobutyl)-2,5-diketopiperazine, which can be formed by (thermal) condensation of the amino acid lysine. Exemplary derivatives include dicarboxylic acid derivatives such as 3,6-di(succinyl-4-aminobutyl)-, 3,6-di(maleyl-4-aminobutyl)-, 3,6-di(glutaryl-4-aminobutyl)-, 3,6-di(malonyl-4-aminobutyl)-, 3,6-di(oxalyl-4-aminobutyl)-, and 3,6-di(fumaryl-4-aminobutyl)-2,5-diketopiperazine. The use of DKPs for drug delivery is known in the art (see for example U.S. Pat. Nos. 5,352,461, 5,503,852, 6,071,497, and 6,331,318, each of which is incorporated herein by reference for all that it teaches regarding diketopiperazines and diketopiperazine-mediated drug delivery). The use of DKP salts is described in U.S. Pat. No. 7,820,676, which is hereby incorporated by reference for all it teaches regarding diketopiperazine salts. Pulmonary drug delivery using DKP microparticles is disclosed in U.S. Pat. No. 6,428,771, which is hereby incorporated by reference in its entirety. Further details related to adsorption of active agents onto crystalline DKP particles can be found in U.S. Pat. Nos. 7,799,344 and 7,803,404, which are hereby incorporated by reference in their entirety.

Drug delivery system: As used herein, “drug delivery system” refers to a system for delivering one or more active agents. U.S. Pat. No. 6,703,381 discloses methods for delivering therapeutic compounds across the blood-brain barrier. This patent is incorporated herein by reference in its entirety for its disclosure related to delivering therapeutic compounds across the blood-brain barrier.

Dry powder: As used herein, “dry powder” refers to a fine particulate composition that is not suspended or dissolved in a propellant, carrier, or other liquid, or appears to be dry to an ordinary person. It is not meant to necessarily imply a complete absence of all water molecules.

Microparticles: As used herein, the term “microparticles” includes particles of micron size range, such as generally 0.5 to 100 microns in diameter, or less than 10 microns in diameter. Various embodiments will entail more specific size ranges. The microparticles can be assemblages of crystalline plates with irregular surfaces and internal voids as is typical of those made by pH controlled precipitation of the DKP acids. In such embodiments the active agents can be entrapped by the precipitation or drying processes or coated onto the crystalline surfaces of the microparticle. U.S. Pat. Nos. 7,799,344 and 7,804,404, both of which are incorporated by reference herein in their entirety, include examples of making suitable microparticles. The microparticles can also be spherical shells or collapsed spherical shells comprising DKP salts with the active agent dispersed throughout. Typically such particles can be obtained by spray drying a co-solution of the DKP and the active agent. U.S. Pat. No. 7,820,676, which is incorporated by reference herein in its entirety, includes examples of suitable spray drying methods. The DKP salt in such particles can be amorphous. The forgoing descriptions should be understood as exemplary. Other forms of microparticles are contemplated and encompassed by the term.

Percent respirable fraction per fill (% RF/Fill): As used herein “% RF/Fill” refers to the amount of powder particles emitted from an inhaler, or drug delivery system, which particles are of size in the respirable range and can be smaller than 5.8 μm, normalized by the total amount of powder filled into inhaler or drug delivery system. In some embodiments, the inhaler can be reusable comprising replaceable cartridges containing the dry powder. In other embodiments, the inhaler is manufactured containing the formulation for single use.

Dry powder formulations of the inhalation systems can comprise active agents for the treatment of acute or chronic pain. In one embodiment, the dry powder formulation can be used for treating pain directly or indirectly associated with central or peripheral nervous system involvement, including, for example, headaches such as migraines; post-operative pain, and pain associated with one or more diseases, including, but not limited to cancer, renal disease, immune disorders including, autoimmune disease, a peripheral neuropathy, a central neuropathy, a traumatic abnormality, a cerebral vascular accident, postoperative pain, dental pain, direct trauma, infection, HIV infection, small pox infection, herpes infection, toxic exposure, exposure to arsenic, exposure to lead, cancer, invasive cancer, congenital defect, phantom limb pain, encephalitis, rheumatoid arthritis, fibromyalgias, spinal root lesions, spinal root impingement, back pain, multiple sclerosis, chronic pain, fibrous tissue pain, muscle pain, tendon pain, ligament pain, pain associated with diarrhea, irritable bowel syndrome, abdominal pain, chronic fatigue syndrome, and spasms, and the like.

In an exemplary embodiment herewith, the method for treating pain comprises providing to a subject an inhalable pharmaceutical composition comprising a dry powder comprising one or more receptor agonist peptides. The receptor agonists can be, for example, alpha-MSH receptor agonists, or opioid receptor agonists, or the like. In one embodiment, the dry powder comprises a diketopiperazine, including, N-substituted-3,6-aminoalkyl-2,5-diketopiperazines. In this and other embodiments, the diketopiperazine can be 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine wherein X—OH is a dicarboxylic acid, for example, X may be fumaryl, succinyl, glutaryl, maleyl, malonyl, oxalyl, or a pharmaceutically acceptable salt thereof.

In one embodiment, the dry powder optionally can contain a carrier molecule and/or pharmaceutically-acceptable excipients, including amino acids including, leucine, isoleucine, glycine, and methionine; surfactants such as polysorbates, and sugars, including mannitol, lactose, trehalose, raffinose and the like. In an embodiment herewith, the analgesic composition comprises one or more receptor agonist peptides and a carrier comprising a diketopiperazine, which composition can be delivered to the patient using a dry powder inhaler.

In one embodiment, the analgesic composition or formulation comprises microparticles. In embodiments the microparticles can comprise a diketopiperazine, for example bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt, and a peptide having an amino acid sequence comprising, for example, less than 30 amino acids, or less than 29 amino acids, or less than 28 amino acids, or less than 27 amino acids, or less than 26 amino acids, or less than 25 amino acids, or less than 24 amino acids, or less than 23 amino acids, or less than 22 amino acids, or less than 21 amino acids, or less than 20 amino acids, or less than 19 amino acids; or less than 18 amino acids; or less than 17 amino acids; or less than 16 amino acids; or less than 15 amino acids; or less than 14 amino acids; or less than 13 amino acids; or less than 12 amino acids; or less than 11 amino acids; or less than 10 amino acids; or less than 9 amino acids; or less than 8 amino acids; or less than 7 amino acids; or less than 6 amino acids; or less than 5 amino acids; or less than 4 amino acids; or less than 3 amino acids; wherein said peptide binds to at least one cell receptor which modulates pain.

In certain embodiments, the analgesic composition comprises an analgesic peptide; wherein the analgesic peptide comprises greater than 5% of the weight of an inhalable dry powder composition and the powder comprises microparticles of an N-substituted-3,6-aminoalkyl-2,5-diketopiperazines. In this embodiment, the diketopiperazine can be 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine, wherein X—OH is a C₂₋₂₀, C₂₋₁₀, or C₂₋₅ dicarboxylic acid, or a salt thereof, for example X may be fumaryl, succinyl, glutaryl, maleyl, malonyl, oxalyl, or a pharmaceutically acceptable salt thereof. In a particular embodiment, the analgesic composition comprises a diketopiperazine having the formula bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt or dipotassium salt.

In a particular embodiment, the compositions comprise peptides or derivatives thereof that, for example, bind to cell receptors, or directly or indirectly affect cell receptor agonists. These cell receptors can include, for example, opioid receptors, alpha-MSH receptors, and the like. In embodiments the opioid receptors can include, for example, a μ opioid receptors, a δ opioid receptors, a κ opioid receptors, combinations of one or more of the receptors thereof, or all three receptors on cells in the central or peripheral nervous systems. In one embodiment, the peptide can be either δ (delta) opioid receptor agonists or μ opioid receptor agonists. In another embodiment, the peptide can bind nonspecifically to δ opioid, μ opioid or κ opioid receptors, or combinations thereof to bring about reduction or abolishment of the sensation of pain. In one particular embodiment, the composition for treating pain comprises a peptide or a peptide derivative which is substantially a κ opioid receptor-selective agonist. In certain embodiments herewith, the κ opioid receptor-selective agonist peptides and/or derivatives thereof can bind selectively to neurons in the peripheral nervous system. In this and other embodiments, the analgesic composition comprises a peptide having an amino acid composition comprising at least three amino acids selected from the group consisting of glycine, alanine, valine, leucine, methionine, threonine, asparagine, glutamine, cysteine, lysine, arginine, histidine, aspartic acid, glutamic acid, phenylalanine, isoleucine, norleucine, tyrosine, serine, proline, and tryptophan. In an aspect of this embodiment, the analgesic peptide comprises at least two amino acids which are phenylalanine groups or derivatives thereof. In an embodiment, the peptide is a tetrapeptide. In an embodiment the tetrapeptide comprises at least one phenylalanine group.

In certain embodiments, the amino acids can be modified, altered, or changed. For example, conservative amino acid changes may be made, which although they alter the primary sequence of the peptide, may not normally alter its function. Conservative amino acid substitutions typically include substitutions within the following groups:

glycine, alanine;

valine, isoleucine, leucine;

aspartic acid, glutamic acid;

asparagine, glutamine;

serine, threonine;

lysine, arginine;

phenylalanine, tyrosine.

Modifications (which do not normally alter primary sequence) include in vivo, or in vitro chemical derivatization of polypeptides, e.g., acetylation, or carboxylation. Also included are modifications of glycosylation, e.g., those made by modifying the glycosylation patterns of a polypeptide during its synthesis and processing or in further processing steps; e.g. by exposing the polypeptide to enzymes which affect glycosylation, e.g., mammalian glycosylating or deglycosylating enzymes. Also embraced are sequences which have phosphorylated amino acid residues, e.g., phosphotyrosine, phosphoserine, or phosphothreonine.

Also included are peptides which have been modified using ordinary molecular biological techniques so as to improve their resistance to proteolytic degradation or to optimize solubility properties. For example, as used herein “dmt” refers to dimethyl tyrosine. Analogs of such peptides include those containing residues other than naturally occurring L-amino acids, e.g., D-amino acids or non-naturally occurring synthetic amino acids. The peptides of the invention are not limited to products of any of the specific exemplary processes listed herein.

In addition to substantially full length polypeptides, the present invention provides for biologically active fragments of the polypeptides.

In an embodiment, the analgesic composition comprises a peptide comprising at least three amino acids selected from: arginine, phenylalanine, leucine, isoleucine, norleucine, tyrosine, serine, proline, and tryptophan.

In an embodiment, the analgesic composition comprises a peptide comprising at least three amino acids selected from: glycine, alanine, valine, leucine, isoleucine, methionine, proline, or phenylalanine.

In an embodiment, the analgesic composition comprises a peptide comprising at least three amino acids selected from: serine, threonine, asparagine, glutamine, tyrosine, cysteine, lysine, arginine, histidine, or aspartic acid.

In an embodiment, the analgesic composition comprises a peptide comprising glutamic acid, arginine, phenylalanine, leucine, isoleucine, norleucine, tyrosine, serine, proline, or tryptophan.

In some embodiments, the peptide lacks glycine.

In some embodiments, the peptide lacks alanine.

In some embodiments, the peptide lacks valine.

In some embodiments, the peptide lacks leucine.

In some embodiments, the peptide lacks isoleucine.

In some embodiments, the peptide lacks methionine.

In some embodiments, the peptide lacks proline.

In some embodiments, the peptide lacks phenylalanine.

In some embodiments, the peptide lacks tryptophan.

In some embodiments, the peptide lacks serine.

In some embodiments, the peptide lacks threonine.

In some embodiments, the peptide lacks asparagine.

In some embodiments, the peptide lacks glutamine.

In some embodiments, the peptide lacks tyrosine.

In some embodiments, the peptide lacks cysteine.

In some embodiments, the peptide lacks lysine.

In some embodiments, the peptide lacks arginine.

In some embodiments, the peptide lacks histidine.

In some embodiments, the peptide lacks aspartic acid.

In some embodiments, the peptide lacks glutamic acid.

In some embodiments, the analgesic compositions can comprise at least one peptide comprising an amino acid sequence of from three to twenty amino acids in length, such as, for example, 3 amino acids in length, or 4 amino acids in length, or 5 amino acids in length, or 6 amino acids in length, or 7 amino acids in length, or 8 amino acids in length, or 9 amino acids in length, or 10 amino acids in length, or 11 amino acids in length, or 12 amino acids in length, or 13 amino acids in length, or 14 amino acids in length, or 15 amino acids in length, or 16 amino acids in length, or 17 amino acids in length, or 18 amino acids in length, or 19 amino acids in length, or 20 amino acids in length, or the like.

In an embodiment, the analgesic peptide comprises at least two amino acids which are phenylalanine groups or derivatives thereof; in a further aspect the phenylalanine residues are adjacent and in a still further aspect the pair of phenylalanine residues is at the N-terminal end of the peptide. In an embodiment, the peptide is a tetrapeptide which comprises at least one phenylalanine group. In an aspect of this embodiment the phenylalanine residue is at the C-terminal end of the peptide, which can be amidated, and is adjacent to a serine residue. In an alternative aspect the phenylalanine residue is at an internal position and is adjacent to an arginine residue.

In some embodiments, the peptide can comprise an amino acid sequence selected from the group consisting of (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1), (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2), Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4); Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), and Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).

In a particular embodiment, a method of treating pain sensation comprises administering to a subject in need of said treatment a therapeutically effective amount of a pharmaceutical composition comprising a pharmaceutically acceptable amount of μ opioid receptor agonist in a composition comprising bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt. In certain embodiments, the pharmaceutical composition can comprise a pharmaceutically acceptable carrier or other inactive agents. In some embodiments, the μ opioid receptor agonist is a peptide that can cross the blood-brain barrier and can bind to the μ opioid receptor in brain cells. In another aspect of this embodiment, the pharmaceutical composition can comprise a δ opioid receptor agonist in the dry powder. In another aspect of this embodiment, the pharmaceutical composition can comprise a κ opioid receptor agonist in the dry powder. In other embodiments, the peptide can be primarily a κ opioid receptor agonist but also bind to either δ (delta) opioid receptors or μ opioid receptors as an agonist. In another embodiment, the peptide can bind nonspecifically to δ opioid, μ opioid or κ opioid receptors, or combinations thereof to bring about reduction or abolishment of pain sensation. In a particular embodiment, the opioid receptor agonist is a tetrapeptide. In some embodiments, for example, the peptide can have an amino acid sequence selected from the group consisting of (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1), (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2), Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4); Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), and Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).

The amount of opioid receptor agonist composition can vary depending on the subject's requirements, for example, in amounts of 1 mg or greater. In example embodiments, the amount of peptide opioid receptor agonist in a dry powder for pulmonary inhalation can be administered in a range of from about 1 to about 50 mg. In one embodiment, the amount of dry powder to be administered can be greater than 50 mg. In some embodiments, the dry powders made by the present method can optionally comprise an amino acid such an aliphatic amino acid, for example, alanine, glycine, leucine, isoleucine, norleucine, methionine at amounts ranging from about 0.5% to about 30% by weight. In one particular embodiment, the dry powder composition comprises the amino acid L-leucine. The opioid receptor agonist composition can further comprise a pharmaceutically acceptable sugar, for example, monosaccharides, disaccharides, oligosaccharides, and the like, including, mannitol, xylitol, lactose, trehalose, raffinose, and the like.

In embodiments, the compositions are effective in treating pain without, or with reduced, traditional opioid side effects, including, respiratory depression, gastrointestinal distress, addiction, somnolescence, tolerance, nausea, constipation, and the like.

In an embodiment, the method provides one or more receptor binding peptides or derivatives thereof to a patient in need of treatment of acute or chronic pain. The method comprises selecting one or more receptor agonist peptides; providing a drug delivery system comprising a composition comprising one or more receptor agonist peptides to a patient, and administering a therapeutically effective amount of one or more receptor agonist peptides in a dry powder. In embodiments the receptor can be, for example, an opioid receptor, or an alpha-MSH receptor, or the like.

In one embodiment, the method comprises administering to a patient suffering with acute or chronic pain and in need of treatment, an analgesic composition of the invention, such as, for example, one comprising a diketopiperazine and a peptide.

In one embodiment, a method is provided comprising providing a drug delivery system for rapid administration of an active agent to a patient with severe pain and in need of treatment and administering the active agent to the subject's circulation. In a particular embodiment, the drug delivery system is designed for drug delivery by inhalation and comprises an inhalation apparatus comprising a dry powder inhaler configured to have a container with a chamber for holding a dry powder in a containment configuration and a dosing configuration, wherein the dry powder comprises a pharmaceutical formulation comprising one or more than one antinociceptive peptides and/or derivatives thereof for immediate delivery of the peptides or derivatives thereof. In one embodiment, the drug delivery system is configured for pulmonary inhalation wherein the dry powder comprises microparticles comprising a carrier molecule and the peptides for delivery to the pulmonary circulation in a therapeutically effective manner. In this and other embodiments, the drug delivery system comprises a dry powder inhaler comprising a container, including a cartridge and a dry powder formulation comprising an antinociceptive peptide.

Disclosed herein are methods and compositions for treating pain with a drug delivery system which can comprise pulmonary delivery. In an exemplary embodiment, the systems can include dry powder inhalers for single or multiple uses, as well as containers, for example, cartridges for dry powder inhalers, and the like.

In particular embodiments herewith, the analgesic composition comprises a diketopiperazine having the formula bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.

In a particular embodiment, a method of treating pain is provided, comprising administering to a subject in need of treatment an analgesic composition comprising a dry powder comprising microparticles of bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine salt, including, the disodium salt, dipotassium salt and any salt produced by a cation which salt has the appropriate solubility, and a peptide selected from the group consisting of (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1), (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2), Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), and Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4).

In embodiments wherein the diketopiperazine is 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine; wherein X is succinyl, glutaryl, maleyl, malonyl, oxalyl or fumaryl; or a pharmaceutically acceptable salt thereof, the composition may be an inhalable dry powder formulation further comprising a pharmaceutically acceptable carrier or excipient, including but not limited to, polysorbates, amino acids, for example, glycine, leucine, isoleucine, methionine; polysaccharides, for example, dextrans; polylactides, polyglycolides, copolymers of polylactide and glycolide thereof, and the like.

In another exemplary embodiment, a method is provided for treating pain, which method comprises providing to a patient a composition comprising an analgesic peptide in an amount greater than 0.25%, 0.5%, 1%, 2%, 5%, 10%, 25% or 50% by weight of the total powder of the microparticle to be administered to the patient; administering to the patient in need of treatment the composition by pulmonary inhalation the peptides using a dry powder inhaler. In one embodiment, the administration is given by oral inhalation with an inhaler for single use and self-administration, the inhaler comprising a container containing the dry powder. The single use, disposable inhaler is manufactured to contain the dry powder composition in containment conditions and wherein the dry powder is exposed to ambient conditions prior to use.

In another embodiment, a method for treating pain comprises the step of administering to the patient in need of treatment, a dry powder composition, comprising a μ opioid receptor agonist, a δ opioid receptor agonist, or a κ opioid receptor agonist, wherein the dry powder composition is administered by pulmonary inhalation of the dry powder composition using a breath powered, dry powder inhaler comprising a cartridge. For example, the inhaler is a multiple use inhaler adapted with a unit dose cartridge containing the dose to be delivered and wherein the cartridge is discarded after use to make room for a new dose. The inhaler can also be configured for a single use and disposable and is manufactured containing the dry powder composition in a single dose. In one embodiment herewith, the dry powder comprises bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine salt, including, disodium salt, dipotassium salt, and the like.

In embodiments described herein, the drug delivery system is non-invasive and has additional advantages over other methods of drug delivery, for example, oral, subcutaneous and intravenous administration of drug products such as proteins and peptides, which products are sensitive to enzymatic deactivation or degradation in the gastrointestinal tract as well as local peripheral and vascular tissue before reaching the target site.

The inhalation system comprises dry powder inhalers which can be breath-powered, compact, reusable or disposable systems, which can have various shapes and sizes, and comprise a system of airflow conduit pathways for the effective and rapid delivery of dry powder medicaments. In one embodiment, the inhaler can be a unit dose, reusable or disposable inhaler that can be used with or without a cartridge as disclosed in U.S. Publication Nos. U.S. 20090308390; U.S. 20090308391, U.S. 2009030392, U.S. 201000197565, which disclosures are incorporated herein by reference for the relevant subject matter they teach. By use without a cartridge we refer to systems in which a container or cartridge-like structures are provided, which are integral to the inhaler, and the inhaler is for a single use and disposable. Alternatively, in some embodiments, the systems comprise a cartridge which is provided separately and installed in the inhaler for use, for example, by the user for self-administration. In this embodiment, the inhaler can be a reusable inhaler and a new cartridge is installed in the inhaler at every use. In another embodiment, the inhaler can be a multidose inhaler, disposable or reusable, which can be used with single unit dose cartridges installed in the inhaler or cartridge-like structures built-in or structurally configured as part of the inhaler; wherein a dose can be dialed in at the time of need.

Embodiments

1. An inhalable, analgesic composition comprising microparticles of a diketopiperazine and a peptide comprising less than 20 amino acids; wherein said composition is effective at relieving pain.

2. The analgesic composition of embodiment 1, wherein the peptide comprises at least three amino independently selected from arginine, phenylalanine, leucine, isoleucine, norleucine, tyrosine, serine, proline, and tryptophan.

3. The analgesic composition of any of the preceding embodiments, wherein the peptide is an opioid receptor agonist.

4. The analgesic composition of any of the preceding embodiments, wherein the peptide comprises an amino acid sequence of from three to eight amino acids in length.

5. The analgesic composition of any of the preceding embodiments, wherein the peptide comprises four amino acids and the composition is for pulmonary administration.

6. The analgesic composition of any of the preceding embodiments, wherein the peptide comprises: (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1), (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2), Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4); Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), or Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).

7. The analgesic composition of any of the preceding embodiments, wherein the peptide binds to a μ opioid receptor, a δ opioid receptor, or a κ opioid receptor, or combinations of receptors thereof, of cells in the central or peripheral nervous systems.

8. The analgesic composition of any of the preceding embodiments, wherein the peptide is a κ opioid receptor agonist.

9. The analgesic composition of any of the preceding embodiments, wherein the composition is a dry powder, and the peptide is at least 0.25% of the weight of the composition.

10. The analgesic composition of any of the preceding embodiments, wherein the composition is a dry powder for inhalation and comprises microparticles having a volumetric mean geometric diameter less than 6 μm in diameter.

11. The analgesic composition of any of the preceding embodiments, wherein the diketopiperazine is an N-substituted-3,6-aminoalkyl-2,5-diketopiperazine.

12. The analgesic composition of any of the preceding embodiments, wherein the diketopiperazine is 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine wherein X is fumaryl, succinyl, glutaryl, maleyl, malonyl, oxalyl, or a pharmaceutically acceptable salt thereof.

13. The analgesic composition of any of the preceding embodiments, wherein the di ketopiperazine is bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5, diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.

14. The analgesic composition of any of the preceding embodiments, wherein the peptide binds a pain-related receptor.

14. A dry powder for pulmonary inhalation comprising the analgesic composition of any of the preceding embodiments.

15. A method for treating pain, comprising administering to a subject in need of treatment a therapeutically effective amount of the analgesic composition of any of embodiments 1-14 using a dry powder drug delivery system comprising a dry powder inhaler configured with a container to hold said analgesic composition in a containment configuration and in a dosing configuration.

16. The method of embodiment 15, wherein the analgesic composition is a dry powder comprising a peptide that binds to an opiate receptor.

17. The dry powder of embodiment 16, wherein the diketopiperazine is bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.

EXAMPLES

The following examples are included to demonstrate certain embodiments disclosed herein. It should be appreciated by those of skill in the art that the techniques disclosed in the examples elucidate representative techniques that function well in the practice of the present invention. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

Example 1 Preparation of Inhalation Powders

Dry powder formulations for inhalation have been prepared from several of these novel tetrapeptide analgesics. Powders containing bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine (FDKP) or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt (Na₂FDKP) and an analgesic peptide were made containing different amount of each peptide, for example, 10% (w/w), 15% (w/w), 25% (w/w) and 50% (w/w) were prepared at 250 mg to 600 mg scale by either lyophilizing a suspension or spray drying a solution.

To prepare inhalation powder containing 15% (w/w) of the tetrapeptide having the amino acid sequence Trp-(D)ser-Ser-Phe-NH₂ (SEQ ID NO: 4), for example, a 10% (w/w) stock solution of the peptide was made (37.49 mg of peptide was dissolved in 337.35 mg of 2% (w/w) acetic acid) and mixed gently into a suspension of FDKP microparticles. The pH of the suspension was adjusted to 4.5 by adding small aliquots of 1:4 ratio of ammonium hydroxide to deionized water. Samples of the suspension mixture were taken for adsorption studies at initial pH value of the suspension, at several pH values during titration and at pH 4.5. Supernatant from the suspension were transferred to filter tubes and centrifuged. The suspension (10 μL) and filtered supernatant samples were transferred into vials containing 990 μL of 100 mM sodium bicarbonate buffer, pH 9.5 for assay by high pressure liquid chromatography (HPLC) analysis. The remaining suspension was pelleted into small crystallization dishes containing liquid nitrogen and lyophilized at 200 mTorr. The shelf temperature was ramped from −45° C. to 25° C. at 0.2° C./min and then held at 25° C. for at least 48 hours during the drying step.

For spray drying, feed solutions were prepared by adding Na₂FDKP, L-leucine, and peptide (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2) to de-ionized water with mixing. The target peptide content of the final powders made was 25% and 50% in the powders. For a target of 25% content, for example, 170 mg of the peptide was used and 408.8 mg of Na₂FDKP, 101.9 mg of L-leucine and deionized water 23.43 g. For a 50% peptide content in the powder formulation, 310.5 mg of peptide, 216.5 mg of Na₂FDKP, 93.4 mg of L-leucine and 23.40 g of deionized water were used. The pH of the feed solutions were 6.95 (25% load) and 5.66 (50% load), respectively. The feed solutions were mixed and the pH adjusted. The solutions were spray dried using the following conditions: inlet temperature of 165° C., outlet temperature of 75° C., aspirator set at 90%, atomization flow using nitrogen gas at 57 mm rotameter, collection point set at high efficiency cyclone, nozzle chiller set at 10° C. and a vacuum pressure of −40 mBar. The suspensions were sprayed dried and samples of the powders were used for analysis using an HPLC method.

Characterization—

Peptide content was assayed using an HPLC method, which utilizes a Waters Alliance 2695 HPLC equipped with a 2487 dual wavelength detector or an Agilent 1200 Series HPLC equipped with a diode array/multiple wavelength detector and 6210 time of flight LC/MS or 6130 quadrupole LC/MS. The samples (5 μL injection each at 8° C.) were analyzed using a Phenomenex Luna Phenyl-Hexyl column (3.0×150 mm, 3 μm) at 30° C. for 45 minutes and at a wavelength of 210 nm using water and trifluoroacetic acid (TFA) at a ratio of 1000 to 1 as mobile phase A and methanol:tetrahydrofuran (THF):TFA (900:100:1) as mobile phase B. Samples were analyzed at a flow rate of 0.3 mL/min. Sample content was determined using a standard sample having a peptide concentration of 1.0 mg/mL and 9 mg/mL FDKP.

Aerodynamic performance of the powders was measured by Andersen cascade impaction (ACI) with dry powders inhalers as described in FIGS. 15C through 15K of U.S. patent application Ser. No. 12/484,125 (US 2009/00308390); Ser. No. 12/484,129 (US 2009/0308391) and Ser. No. 12/484,137 (US 2009/0308392), which disclosures are incorporated herein by reference for their teaching of the relevant subject matter. Particle size distribution was measured by a laser diffraction method using a Sympatec RODOS M powder disperser as described in U.S. patent application Ser. No. 12/727,179 (U.S. 2010/0238457); which disclosure is incorporated herein by reference for its teaching of the relevant subject matter. Moisture content was also measured by thermogravimetric analysis (TGA) and particle morphology was examined by field emission scanning electron microscopy (SEM).

Adsorption Study—

Samples from different batch preparations of five different peptides prepared by the lyophilization method were analyzed. The supernatant samples were transferred to 1.5 mL, 0.22 μm filter tubes and centrifuged. The suspension and filtered supernatant samples (500 μL each) were transferred into 50 mL volumetric flasks and brought to volume with 100 mM sodium bicarbonate buffer, pH 9.5. The solutions were transferred to suitable vials for assay and analysis by HPLC. The results are shown in Table 1 below from lyophilized powders. Samples 1, 2, 3, 4, and 5 represent samples taken from five different batches of inhalation powders prepared using five different, unique peptides.

TABLE 1 Attribute Peptide Powder Sample No. 1 2 3 4 5 MKC Lot # A B C D F Peptide Assay (% peptide) 15.2 14.9 15.0 13.7 15.9 Aerodynamic RF/fill 46.5% 63.2% 68.3% 52.3% 54.3% performance by ACI CE 99.0% 98.3% 96.9% 99.7% 97.1% (Gen2C) Extent of Initial  4.7% * * 34.5%  0.5% adsorption (pH) (pH 3.9) (pH 3.9) (pH 3.5) (pH 3.5) (pH 4.0) Final  4.2%  6.5% 18.9% 13.9%  6.5% (pH 4.5) * Indicates adsorption was measured at less than zero

The data in Table 1 illustrate that the target peptide content intended (15%) correlates with the results obtained in each batch of inhalation powder made. The data also indicate the excellent aerodynamic performance for each inhalation powder since at least 45% of the powder filled in the cartridge is delivered in the respirable range (RF/fill>45%), wherein greater than 96% of the cartridge powder content is emitted from the inhalers tested. The data also show that adsorption of the peptide onto the FDKP varied depending on the peptide, from 4.2% for Sample No. 1 to 19% for Sample No. 3 at pH 4.5.

The chromatograms from the HPLC analysis resolved two peaks when compared to the standards, i.e., a peak corresponding to FDKP and a second peak corresponding to the peptide under analysis for each of the powders made. USP resolution values for each FDKP-peptide pair ranged from 11.83-33.50 indicating excellent resolution. Tailing factors calculated ranged from 1.81-2.32 indicating asymmetric peak shape for peptides Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4), Ac-His-(D)Phe-Arg-(D)trp-Gly-NH₂ (SEQ ID NO: 6), and (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1) at 1 mg/mL.

FDKP-peptide solutions were kept at room temperature for 19 days to evaluate stability. There was substantially no degradation observed for all peptides in solution with FDKP during the experiment.

Peptide content of the powders made using Na₂FDKP was measured using the HPLC method, and data from ACI aerodynamic performance of the powders are provided in Table 2 below.

TABLE 2 Peptide X₅₀ ++ (μm) Assay (%) Sample % LOD 3.0 Dry ID % RF/fill % CE* (TGA)** 0.5 bar bar As-is basis 1 41.7 87.0 7.98 2.7 2.4 25.3 27.5 2 43.8 87.6 8.06 3.3 2.4 46.9 51.0 *CE denotes cartridge emptying or content released from inhaler in use from total. **LOD denotes content loss on drying from original amount ++ X₅₀ denotes volumetric mean geometric diameter

Table 2 data illustrates that the ACI data for the two powders containing 25% and 50% peptide content prepared with Na₂FDKP were similar with respect to respirable fraction in the total powder content of the inhaler tested. That is, one powder formulation yielded about 42% RF/fill with 87% of powder content in the test inhaler/cartridge system was emitted using a batch powder having 25% content of (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2). For the powder having 50% peptide content, the powder produced a 44% RF/fill with 88% of the powder content emitted from the inhaler during testing. Median size of the primary particles (3.0 bar dispersing pressure) was 2.4 μm for both powders. At a low dispersing pressure (0.5 bar) the powder with 50% peptide content had a slightly higher degree of agglomeration than the powder having a peptide content of 25%, i.e., the high content powder had 3.3 μm median particle size with 79% of the particles measured less 5.8 μm, compared to 2.7 μm with 86% of the particles measure less than 5.8 μm. SEM images show shriveled (raisin-like) particles, some with visible openings which display the inner hollow core and shell of the particles.

Example 2 In Vivo Experiments Using FDKP-Peptide and Na₂FDKP-Peptide Compositions

Antinociceptive effect was tested in a mouse tail-withdrawal (“tail-flick,” Aldrich et al. 2009) assay in which the tail of a restrained mouse is exposed to water at 55° C. The longer the latency until the mouse flicks its tail away from the water, the more effective the antinociceptive effect of the peptide. There is a time limit to the test and any animal that does not flick its tail (“Tail-flick test”) before the time limit is reached is subject reaching this time limit is recorded as demonstrating a 100% effect. Durations shorter than the maximum are reported as a percentage of the time limit. This tail-flick test (also known as the 55° C. warm-water tail withdrawal assay) is an industry acceptable, nonclinical model for assessing the efficacy of analgesics in treating acute pain. To test placebo effect, FDKP (TECHNOSPHERE®) powder (0.5 mg) without any peptide was used in the study. Each animal is tested for baseline tail-withdrawal latency prior to drug administration. Latency to withdraw the tail was subsequently measured in 10 minutes post-drug administration intervals as indicated. A maximum response time of 15 seconds was utilized to prevent tissue damage. Data reported as percent antinociception, as calculated by the following equation: % antinociception is equal to 100 times (test latency minus baseline latency) divided by (15 minus baseline latency).

The tetrapetide, (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2) was administered to mice by intraperitoneal (i.p.) injection (3 mg/kg) in a saline solution, and by pulmonary insufflation of a dry powder formulation containing FDKP at various doses, 0.25 mg, 0.125 mg, 0.013 mg, 1.25 μg and 0.13 μg. The tail-flick test was performed for a period of time after administration. The results of the study are shown in FIG. 1 as antinociception effect versus time (dose response). The data show that all doses of the tetrapeptide rapidly provided near-complete antinociception. The effect of the i.p. injection decayed almost linearly with time. When insufflated, the effect was saturated at higher doses with a plateau of approximately 30 minutes at the 0.125 mg dose and 50-55 minutes at the 0.25 mg dose. The results show a clear dose response was evident for the peptides used. Placebo powder produced a negligible effect on nociception.

Example 3

Experiments were conducted similarly as described in Example 2 above. In this study, a different tetrapeptide, (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1, Compound 1) was administered to mice using i.p. injection of 1 mg/kg in saline solution. For insufflation studies, insufflation powder comprising Na₂FDKP having varying peptide content (25%, 2.5%, 0.25%, and 0.025%) was administered to mice in a powder dose of 0.5 mg. For the 2.5%, 0.25%, and 0.025% results, the powder containing 25% peptide content made as described in Example 1, above, was diluted with blank FDKP powder to obtain the lower peptide content samples. The results are shown in FIG. 2. The data show the insufflated tetrapeptide (Compound 1) powders provided a rapid antinociceptive effect that was saturated at the highest dose with a plateau lasting approximately 40 minutes. At lower doses, the effect was not saturated but showed a dose response. The injected peptide (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1) had the longest duration of effect, but did not have the same rapid onset as the insufflated doses.

Example 4

Experiments were conducted similarly as described in Examples 2 and 3 above. In this study, a dry powder formulation containing tetrapeptide (D)Phe-(D)Phe-(D)Ile-(D)Arg (SEQ ID NO: 1, Compound 1) was administered to mice. A subset of mice was administered an intraperitoneal dose of morphine 10 mg/kg (AUC 6795) of body weight. In addition, one group of mice received an i.p. injection of saline solution; one group received 0.25 mg of blank FDKP/TECHNOSPHERE® powder by insufflation as controls. Another group of mice received 0.125 mg of morphine by insufflation; one group of mice received a powder formulation containing 0.125 mg of peptide (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1) and one group of mice received a powder formulation containing 0.125 mg of peptide (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2) by insufflation. The mice were monitored for activities related to side effects of morphine and peptide administration, specifically changes in spontaneous locomotion and respiration rates.

Powder was administered to mice by insufflation at 5 mg/kg of body weight. The responses in the 55° C. warm-water tail withdrawal assay were examined for two hours. The results are shown in FIG. 3. The data demonstrate that insufflated powder inhibits nociception faster than injected morphine (squares). The duration of action of the tetrapeptide on pain (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1, Compound 1, triangles) and morphine sulfate is similar. Morphine is known to induce locomotor hyperactivity in mice and depress the rate of respiration. In a comparison study of inhalable morphine powder (triangles) and dry powder formulations comprised of tetrapeptides (Compounds 1 and 2 (squares)) administered by insufflation, these effects were observed in mice administered morphine. In contrast, the ambulation and respiration rates (FIG. 4A, FIG. 4B, respectively) of mice receiving the tetrapeptide powder were comparable to animals receiving placebo (FDKP blank, circles) powder as shown in the figures.

Example 5

In a conditioned place preference (CPP) study to evaluate the “reward” or “aversive” value of the drug, mice are conditioned to associate one compartment of the apparatus with treatment. The apparatus itself is “balanced,” meaning that mice show no initial preference for one chamber over another (FIG. 5, left-most bar). Reinforcing agents result in an increased place preference for the drug-paired compartment, whereas aversive agents result in a decreased place preference. The experiments were conducted similarly as described in the previous examples. Mice were insufflated with 0.125 mg of morphine or powder formulations containing 0.125 mg of tetrapeptide (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1, Compound 1) or (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2). To test placebo effect, additional mice were insufflated with FDKP (TECHNOSPHERE®) powder (0.5 mg) without any peptide. The results of these experiments are shown in FIG. 5. The data show that mice insufflated with the placebo powder or the powder containing the tetrapeptide (D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1, Compound 1) or (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2) showed no preference for the paired compartment. In contrast, mice treated with morphine exhibited a strong preference for the associated compartment, confirming the expected reward effect provided by the drug.

Accordingly, dry powder formulations for inhalation comprising peptides can provide opioid-like pain relief with fewer adverse effects than current, commercially available analgesics. The inhalation powder has been administered to mice by pulmonary insufflation. In a nonclinical model of acute pain (the 55° C. warm-water tail withdrawal assay), the dry powder formulations comprising the peptides demonstrated analgesic activity comparable to injected morphine without the typical opioid side effects. Unlike mice treated with morphine, those given the dry powder formulations comprising the peptides surprisingly did not exhibit depressed respiration or alterations in spontaneous locomotor activity. Nor did they exhibit a place-conditioning response, a behavior associated with a “reward” after receiving the FDKP/opioid receptor agonist peptide dry powder formulation.

Example 6

A 48 yr. old female patient reports headache pain to her doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing a FDKP/SEQ (D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2) composition prepared as described in the previous Examples. The analgesic composition is 15% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 5 mg/kg of body weight. The patient reports the elimination of her headache pain.

Example 7

A 22 yr. old male patient undergoing chemotherapy reports stomach pain to his doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing a FDKP/(D)Phe-(D)Phe-(D)Ile-(D)Arg-NH₂ (SEQ ID NO: 1, Compound 1) composition prepared as described in the previous Examples. The analgesic composition is 15% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 5 mg/kg of body weight. The patient reports the elimination of his stomach pain.

Example 8

A 63 yr. old female patient reports back pain to her doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing a FDKP/Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3, Compound 3), composition prepared as described in the previous Examples. The analgesic composition is 15% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 4 mg/kg of body weight. The patient reports the elimination of her back pain.

Example 9

A 28 yr. old male patient reports dental pain to his doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing an Na₂FDKP/Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6, Compound 6) composition prepared as described in the previous Examples. The analgesic composition is 10% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 7 mg/kg of body weight. The patient reports the elimination of his dental pain.

Example 10

A 33 yr. old female patient reports pain due to multiple sclerosis to her doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing an Na₂FDKP/(D)Phe-(D)Phe-(D)Nle-(D)Arg-NH₂ (SEQ ID NO: 2, Compound 2) composition prepared as described in the previous Examples. The analgesic composition is 20% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 3 mg/kg of body weight. The patient reports the elimination of her multiple sclerosis pain.

Example 11

A 58 yr. old male patient reports muscle pain to his doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing a FDKP/Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6, Compound 6) composition prepared as described in the previous Examples. The analgesic composition is 15% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 5 mg/kg of body weight. The patient reports the elimination of his muscle pain.

Example 12

An 8 yr. old male patient reports pain from a broken arm to his doctor. Following examination of the patient, the doctor prescribes an analgesic composition containing a Na₂FDKP/Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4, Compound 4) composition prepared as described in the previous Examples. The analgesic composition is 25% peptide. The analgesic composition is administered with a reusable inhaler calibrated to provide a dose of 2 mg/kg of body weight. The patient reports the elimination of his pain.

Example 13

A 55 yr. old female patient reports her low pain threshold to her dentist. Following examination of the patient and prior to the dental procedure, the dentist administers an analgesic composition containing a FDKP/Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7, Compound 7) composition prepared as described in the previous Examples. The analgesic composition is 10% peptide. The analgesic composition is administered with a single-use inhaler designed to provide a dose of 5 mg/kg of body weight. The patient reports no pain during the dental procedure.

While the invention has been particularly shown and described with reference to particular embodiments, it will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printed publications throughout this specification. Each of the above-cited references and printed publications are individually incorporated herein by reference in their entirety.

In closing, it is to be understood that the embodiments of the invention disclosed herein are illustrative of the principles of the present invention. Other modifications that may be employed are within the scope of the invention. Thus, by way of example, but not of limitation, alternative configurations of the present invention may be utilized in accordance with the teachings herein. Accordingly, the present invention is not limited to that precisely as shown and described. 

We claim:
 1. An inhalable analgesic composition comprising microparticles of a diketopiperazine and a peptide comprising less than 20 amino acids; wherein said composition is effective at relieving pain.
 2. The inhalable analgesic composition of claim 1, wherein the peptide comprises at least three amino acids independently selected from arginine, phenylalanine, leucine, isoleucine, norleucine, tyrosine, serine, proline, and tryptophan.
 3. The inhalable analgesic composition of claim 2, wherein the peptide is an opioid receptor agonist.
 4. The inhalable analgesic composition of claim 2, wherein the peptide is an amino acid sequence of from three to eight amino acids in length.
 5. The inhalable analgesic composition of claim 4, wherein the peptide is a four amino acid sequence and the composition is for pulmonary administration.
 6. The inhalable analgesic composition of claim 4, wherein the peptide comprises: Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4), Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), or Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).
 7. The inhalable analgesic composition of claim 1, wherein the peptide binds to a μ opioid receptor, a δ opioid receptor, or a κ opioid receptor, or combinations of receptors thereof, of cells in the central or peripheral nervous systems.
 8. The inhalable analgesic composition of claim 1, wherein the peptide is a κ opioid receptor agonist.
 9. The inhalable analgesic composition of claim 1, wherein the composition comprises a dry powder, and the peptide comprises at least 0.25% of the weight of the composition.
 10. The inhalable analgesic composition of claim 1, wherein the composition comprises a dry powder for inhalation and comprises microparticles having a volumetric mean geometric diameter less than 8 μm in diameter.
 11. The inhalable analgesic composition of claim 1, wherein the diketopiperazine is an N-substituted-3,6-aminoalkyl-2,5-diketopiperazine.
 12. The inhalable analgesic composition of claim 1, wherein the diketopiperazine is 2,5-diketo-3,6-di(4-X-aminobutyl)piperazine.
 13. The inhalable analgesic composition of claim 11, wherein the diketopiperazine is bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5,diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.
 14. A dry powder for pulmonary inhalation comprising the inhalable analgesic composition of claim
 13. 15. A method for treating pain, comprising administering to a subject in need of treatment a therapeutically effective amount of an inhalable analgesic composition comprising microparticles of a diketopiperazine and a peptide comprising less than 20 amino acids using a dry powder drug delivery system.
 16. The method of claim 15, wherein the dry powder drug delivery system comprises a dry powder inhaler comprising a container configured to hold said inhalable analgesic composition in a containment configuration and in a dosing configuration.
 17. The method of claim 15, wherein the inhalable analgesic composition comprises a dry powder comprising a peptide that binds to an opiate receptor.
 18. The method of claim 17, wherein the diketopiperazine is bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5, diketopiperazine, or bis[3,6-(N-fumaryl-4-aminobutyl)]-2,5-diketopiperazine disodium salt.
 19. The method of claim 17, wherein the peptide comprises: Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4), Dmt-D-Arg-Phe-Lys-NH₂ (SEQ ID NO: 5), Ac-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO: 6), or Ac-Nle-Gln-His-(D)Phe-Arg-(D)Trp-Gly-NH₂ (SEQ ID NO:7).
 20. The method of claim 17, wherein the peptide binds to a μ opioid receptor, a δ opioid receptor, or a κ opioid receptor, or combinations of receptors thereof, of cells in the central or peripheral nervous systems.
 21. The inhalable analgesic composition of claim 12, wherein X is fumaryl, succinyl, glutaryl, maleyl, malonyl, oxalyl, or a pharmaceutically acceptable salt thereof.
 22. The inhalable analgesic composition of claim 1, further comprising one or more pharmaceutical carrier or excipients selected from amino acids, sugars, and surfactants.
 23. The inhalable analgesic composition of claim 22, wherein the amino acids comprise at least one of leucine, isoleucine, glycine, and methionine.
 24. The inhalable analgesic composition of claim 22, wherein the sugars comprise at least one of mannitol, lactose, trehalose, and raffinose.
 25. A synthetic peptide having an amino acid sequence Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3).
 26. A synthetic peptide having an amino acid sequence Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4).
 27. An inhalable analgesic composition comprising a diketopiperazine, a synthetic peptide having an amino acid sequence Trp-(D)Pro-Ser-Phe-NH₂ (SEQ ID NO: 3), and optionally, a pharmaceutically acceptable excipient.
 28. An inhalable analgesic composition comprising a diketopiperazine, a synthetic peptide having an amino acid sequence Trp-(D)Ser-Ser-Phe-NH₂ (SEQ ID NO: 4), and optionally, a pharmaceutically acceptable excipient. 